1. Field of the Invention
The present invention relates to a technique for generating a two-dimensional graphics image.
2. Description of the Related Art
A case will be examined below wherein when a two-dimensional graphics rendering result is laid out on a three-dimensional space, a vision of the space from a certain point on this space is to be output to a plane such as a display. In this case, three-dimensional affine transformation has to be applied to a bitmap image obtained by rendering the two-dimensional graphics image to lay it out on the space, and perspective transformation has to be applied to project the image onto the plane. However, such three-dimensional deformation processing takes much time. In addition, since the three-dimensional deformation processing and perspective transformation processing are applied to the bitmap image, the image quality of the bitmap image deteriorates compared to that rendered as a two-dimensional graphics image. For this reason, the following conventional method has been proposed (see Japanese Patent Laid-Open No. 8-263690 (patent reference 1).
In the conventional method, both three-dimensional structure data and two-dimensional image data are stored. When the stored two-dimensional image data is usable, it is used without generating any two-dimensional image data from the three-dimensional structure data.
However, the conventional method executes a process including space layout by means of the three-dimensional deformation processing and projection processing onto the plane for a bitmap image obtained by rendering a two-dimensional graphics image. For this reason, the image quality of the output result drops compared to the direct rendering result of the two-dimensional graphics image. Also, the method of patent reference 1 cannot be applied when a relative relationship between a viewpoint and object has changed.